In-vivo Clearance of 125I-Aβ40 via BEI Method

The in-vivo 125I-Aβ40 (PerkinElmer; Boston, MA, USA) clearance was investigated using the brain efflux index (BEI) method as we described previously [20 (link)]. In brief, at the end of the treatment, animals were intraperitoneally anesthetized with xylazine and ketamine (20 and 125 mg/kg, respectively), followed by the insertion of a stainless-steel guide cannula into the right caudate nucleus, an area rich with blood microvessels, of the mice’s brain following previously established protocols [58 (link)]. A tracer fluid (0.5 μL) containing 125I-Aβ40 (30 nM; PerkinElmer, MA, USA) and 14C-inulin (0.02 mCi, American Radiolabeled Chemicals, St. Louis, MO, USA), prepared in an artificial extracellular fluid buffer (ECF; 122 mM NaCl, 25 mM NaHCO3, 3 mM KCl, 1.4 mM CaCl2, 1.2 mM MgSO4, 0.4 mM K2HPO4,10 mM D-glucose, and 10 mM HEPES, pH 7.4), was microinjected in the mice brains. Thirty minutes later, the brains were rapidly collected for a 125I-Aβ40 analysis. 125I-Aβ40 and 14C-inulin radioactivity was determined in the brain tissues using Wallac gamma and beta counters (PerkinElmer Inc. Waltham, MA, USA), respectively. 125I-Aβ40 BEI was determined using the formula: